Interestingly, I have seen only one place where there is a sewer drain in an elevator (this is quite near where I live, in an administration centre of modernist

Interestingly, I have seen only one place where there is a sewer drain in an elevator (this is quite near where I live, in an administration centre of modernist concrete design). Judging by the smell, it's very necessary. Never thought how it works, but I presume the elevator needs to have a storage tank underneath the cage, and that needs to be emptied regularly.